1. Field of the Invention
This invention relates to the production of wax trees for casting and, more particularly, to the design of blades or knives for heating wax runners and wax pattern gates to attach the wax pattern gate to a wax runner.
2. Prior Art
The Lost Wax Process is a long established process for casting. In the practice of the Lost Wax Process a wax pattern of a part to be cast is molded in wax. When the wax pattern is molded, a pattern gate is molded with the wax pattern in one piece. Wax runners are also molded separately. Wax runners are usually at least one branch frequently with flat surfaces and two ends. Some wax runners have a circular cross section and thus do not have either flat surfaces or edges. At one end of the runners there is a head and the other end there is a tail. A pour cup may be located at the head. The wax pattern gates are affixed to the wax runners to form a wax tree. To do this both ends of the wax pattern gate and the surface of the wax runner need to be heated sufficiently to melt wax to permit fusion. Once the wax patterns are affixed to the wax runner, a wax tree has been formed, and then ceramic material is placed on the wax tree. Once the ceramic has hardened it is heated causing the wax to flow out of the ceramic. The ceramic thus forms a mold into which the molten metal is poured to produce the desired part.
In recent times, much of the Lost Wax Art has been substantially automated. In the patent application of Ludwig, et al, entitled Process and Apparatus for the Assembly of Wax Trees, Ser. No. 10/304,840, assigned to the same assignee, an advanced process and apparatus is taught for automating the fusion of wax gates of wax patterns 5 to a wax runner. A heated blade is used to heat the pattern gates and the wax runner. The heated blade, the pattern gates and the wax runner are all operated by robotics. However, the fusion of wax pattern gates to a wax runner has been traditionally a manual operation performed by heating putty knives on a Bunsen Burner to melt the surface of the wax runner and the end of the pattern gate.
In the automated process, the wax runners are held by a head stock and a tail stock in a runner station. The wax runner is also heated in the automated process so that a plurality of wax patterns can be affixed to the wax runner at one time.
Maintaining a wax runner in a perfectly flat position when attaching the wax patterns is a most desirable goal, but unfortunately is not readily attainable. As a result, portions of the wax runner are penetrated more deeply by the heated blade than other portions. Excess molten wax is a result of excessive melting, and should the excessive melted wax run over the side of the wax runner, the wax runner and the wax patterns attached to it are not useable resulting in lost product.
In heating the wax gate and the wax runner, the temperatures of heating the wax can become sufficiently high as to exceed the flash point of the wax causing it to give off fumes which are considered to be a health hazard.
Therefore, it is highly advantageous to provide a blade for heating the wax runner which prevents molten wax from running over the edge of a wax runner, and it is also highly desirable to control the temperature of melting of the wax gate and wax runner to avoid the emission of fumes.
Therefore, the objects of this invention are to provide the following:
a knife for melting wax on a wax runner which prevents molten excess wax from flowing over the side of the wax runner by providing space in the surface of the knife to retain molten wax.
a knife which conforms the heated area to the configuration of the end of the wax gate of the wax pattern, to eliminate the melting of unnecessary wax.
a knife which reduces the incidence of lost wax trees.
a knife which is economical to produce and which is durable and dependable.
a knife whose temperature is controlled to prevent the formation of undesirable fumes by maintaining the temperature of the knife below the flash point temperature of the wax.